Temperature and its effect on airlocks

A few days ago, under a thread with the banner "Wine Aging" I made some comments about the effect of temperature on the ability of airlocks to protect wine. I promised to post more later.

Air locks are designed to be a constant pressure valve to protect the wine. Of course during fermentation CO2 is given off, the pressure in the vessel tries to go up and the excess volume bubbles out through the airlock. Perfect. If the temperature of bulk aging wine increases, the wine expands, pressure tries to goes up, and what ever is in the head space bubbles out through the airlock. Fine. If the wine expands too much and all the head space is expelled, then wine goes out through the airlock. Not so fine. You can watch your wine you can prevent this.

But if the temperature drops too much, a different scenario takes place. Outside air will bubble through the airlock into the carboy. If this happens it is not a very good thing. So how much protection does an airlock provide and how important is this?

I checked two types of airlocks. The S shaped airlock with three bubble chambers on each side will hold 11 cc's of liquid when properly filled. The

3 piece cylindrical airlock will hold 9 cc's from bottom of the floating valve to where liquid spills through the tube so it provides 9 cc's of protection. (I did not have one of the S locks with one chamber on each side free to test.) For this analysis I will use the 9 cc smaller airlock

The question now is how much of a temperature change will these volumes protect against before air bubbles through the airlock. This is effected by the volume of the wine and the starting temperature. I assume 25 deg C as the starting temperature and determined the temperature drop the airlock will protect against for different size carboys. I found the following:

Carboy Temp Drop (US gal) (deg C) 1 9.7 3 2.2 5 2.0 6 1.2 10 0.8 12 0.7 13 0.6

This shows some pretty small numbers, but what are the restrictions of the calculation.

1) I used the expansion of water. I found the expansion table for alcohol but not for 13% alcohol, so I considered water to be a better estimate. I suspect that wine will have more expansion and therefore less protection but I can not say for certain. 2) I do not make a correction for expansion of the glass vessel but this should be very small. 3) This is based on temperature changes of the wine, not the room. Over a one day/night temperature cycle the room may change more than the wine. (Thanks to Jack Keller for pointing this out.)

Now what does this mean? Standard airlocks will protect carboys of 5-6 gal or smaller from temperature changes in a temperature controlled home and may well protect the larger carboys. But if you are keeping wine in an unairconditioned room or in a cellar that sees temperature changes of several degrees C. You may want to take all this into account.

You should be aware of day to night temperature changes, changes associated with cold fronts, and seasonal changes. Seasonal changes, though they may cause the largest change will probably not be too important as there will only occur once a year. Day night changes may not be important as the wine may not change temperature fast enough to matter. But if it does it will be catastrophic as it will happen 365 times a year. Changes associated with cold fronts and heat waves may be the ones you really have to be concerned about.

Ray Calvert

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Ray
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Hi Ray

Thanks for bring light to this risk. After reading your post I placed a 12 Gal DJ for cold stabilization. I left about and inch of headspace. The temperature in my MLF area is 70F and in the garage it is 40F. I was amazed at how much volume contraction occurred.

I am wondering whether I should now adjust the headspace or leave it for the

3-4 weeks it will take to cold stabilize?

Joe

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Joe Ae

Adjust the head space or blow it out with inert gas.

Ray

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Ray

Joe, I ditto your thanks to Ray for the numbers. Ray is very good with the science and math and I appreciate his input. We may disagree on what it means under given circumstances, but I do not dispute the physics or the math.

To your question, I would again say (as in the previous thread on bulk aging) that if your wine was appropriately sulfited the increased ullage from the wine's contraction will not matter to your wine. I would leave it alone so that when you bring the wine back indoors it can expand back to its former level. If you top up now, you will have to later remove what you added or pay the consequences.

Jack Keller, The Winemaking Home Page

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Jack Keller

Ray, I echo Joe's thanks. The raw numbers ought to be a concern to everyone who doesn't have a tight reign on the temperature of their winemaking and storage areas, especially if you bulk age in containers larger than 5 gallons.

I've been thinking about these numbers since you shared them with me a few days ago. I kept thinking of your comment to me that they indicate a larger airlock is really needed for larger containers. I couldn't help but think of how we used to make our airlocks before they were so readily and cheaply available and I think the old method might serve anyone who thinks they might have a problem. All one needs are an appropriately sized drilled bung, a length of 1/4 inch tubing and a quart jar with lid--metal or plastic. You will need an electric drill and probably some silicon gel caulking .

The bung must fit your demijohn or carboy correctly. Drill a hole in the lid of the quart jar as close to the exact diameter of the 1/4 inch tubing as you can get. An inch or so from that hole drill a very small hole. It need not be larger than 1/16th inch. If the lid is metal, you can prick a hole in it with a small nail. Insert one end of the tubing into the demijohn or carboy bung but do not push it past the lower edge of the bung itself. If the fit is not tight, seal it with the silicon. Trim the tubing so it arches upward and over to the bottle (presumably sitting next to the demijohn or carboy), through the larger hole in the lid, and about 2/3 down into the quart jar. Fill the jar 3/4 full of 10% sulfite solution, tighten the lid, and seal the tubing/lid junction with silicon. When the silicon dries, you have an airlock that can withstand a dozen degrees of temperature change either way.

Jack Keller, The Winemaking Home Page

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Reply to
Jack Keller

Thanks for the kind words, Jack. It is not that we disagree, we are interpreting the numbers based on different situations. The reason information sometimes seems so conflicting on this site is that we are all developing techniques that apply to the overall method each of us use. Take one step from an overall procedure that makes good wine and try to stick it into another method and it may not work. What is important is to develop an overall understanding of what is going on so you can determine whether a persons suggestion will work for you. If you protect your wine with good levels of sulfite and let some air get to it, it may not matter. If you are making wine with no sulfite, it may be disastrous. We just need to be award of what is happening overall.

You are right about making your own airlocks and I have been planning to make one for my 13 gal carboy. Just have not got around to doing it even though I REALLY believe I should.

Ray

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Ray

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